Radio antenna



7 QB; WATTS, JR, ETAL 2,436,843

RADIO ANTENNA Match 2, 1948.

' Filed July 9/1943 3 Sheets-Sheet 1 INVENTORS CHESTEE a. WA775 an,

LEON H/MMEL ATZURAEY' March 1948. c. s. WATTS, JR, ETAL- 2,436,843

RADIO ANTENNA Filed July 9, 1945 v 3 Shets-Sheet 2 INVENTORS CHESTER B. WATTS JR.

. ATTORNEY Patented Mar. 2, 1948 zfi qfii i 4 mo Ghest'er B; Waiter! East Orange, N. J., and Leon'flimmei, York, N. Y., assignors to Federal "Telephone ani- Radio Corporation, Newark, N. 1.,- mpbtation of Delaware Aponeat' onmiy e, 194?, Serial No. 494,040"

7 SW; (Cb (250* l1) This invention reiates to radio antennas and in particular to directive antennas for operation Y at u'itra-high frequencies. i

An object of the invention is to provide a unitary antenna struoturefor operationat-ultra high frequencies, 7

Another object oithe invention is to providea directional antenna structure for radiating predominantly horizontaiiy poiaiized waves.

, A further-object of the invention is to provide a, directionai antennastructure for adiating.hor-- izontaiiy polarized waves whose energy is concentrated in a substantiaiiy horizontal plane.

A stili further object of the invention is to provide an antenna system suitable tor operation with a ortable gii-de path transmitter.

These and other objects and features or our invention wi'il be best understood 'fromthefoilowing description of an embodiment thereof and as illustrated in the accompanying'cirawing's in m I v v, H

antenna sy'sterri. Betweenthe supportingmer-n- Figs. I and 2 are partiaiiy seetionali'zed jpian and elevationa-i views respeotiveiy of the antenna system of our invention. f

Fig. 3 is a partially sectionaiized view of the antenna structure as viewed-from the plane 1 4 or Fig. 2, and I Fig. 4 illustrates a constant intensity *fieidpab tern in the horizontal plane resulting iromradi ation from our antenna structure.

The antenna structure of our invention is pan tiouIari-y useful in connect-ion with portable instrument' landing equipment such as is described in U. S. Alford Patent 2,294,882. This'patent flee scribes an antennasystem for establishingasflit able glide path for the landing of aircraft in which two antennas are positioned one abovethe other in a manner such that thefiei-d patterns of thetwo antennas combine to produce the glide path. Both antennas operate onthe same carrier (7 2 path, This problem of reradiation is very inimutant in connection with poi-table equipment sincean otherwise suitabie Io'oation for a landing runway may "be rendered nnsuitabie due to the reflections from objects located on the far side of'the transmitter with respect to the runway.

with the antenna structure of our invention, the field pattern which determines the glide path extends suh-stantiaiiy from one side oniy of the antenna-and since there is httie or no radiation frorn'the opposite sidethepfehiem oi undesired reflections doesnotexist.

Referring now comes. 1 and 2, the reference oharacter' 2 represents a wooden mast or other supoorting means *for our antenna structure. A rectanguiar frame member-composed of a spooing membero. two supporting members 8 and in; and ajtuouiar member. r1 su ported on the mast 2 by two'ci amping' devices Hand to serves to mount the active radiating elements of our hers! and romaine tubular member I 2 are frequency, but the radiation from each antenna is modulated at its own characteristic frequency and roduces what-is termed an equi-signai giide path. The antenna arrangement of our invention is particuiarly satisfactory'for determining one of the fleld patterns of the glide path.

In'the Alford patent above're'ferred'to-,'th radiation patterns resulting from each of thean, tennas disclosed therein are symmetrical, that is to say, the intensity of the radiated fieldis soostanti'aliy equal in any two opposite directions from either antenna structure. However, the field pattern on one side only of the antenna system is employed for determining the: glid'e'p'atti. The energy radiated from the opposite-sided the antenna represents waste-d energy, and fi'ir--- thermore, should there be an obstaclesin the fieldof this energmrefleotedradiation therefrom may produce deleterious effects such as undesired lobes of energy in the 'fie'id oith'e desired glide positioned two junction boxes to and m. These function hoses may area be: considered as part of the-supportingst'ruoture and are-forthe' purpose of 'assem'bling' radiating antenna arms and a transmission line feeding to said arms for energizing same;

Two-heritantennaarrns Hand 18 are mounted on the junction box Win the manner shown bya 'sectiona-Iized portion of'Fie. I. Referring to seetioii-afized' portion, an insn'iating' member 26 having a; reduced-portion 28 isspre'ss'ed firm-Ty within the tubuIar antenna arm 22. A not 30 firmIy' clamps the antenna" arm and. insulatingmember 26 to the junction-box was iiiustrated. The Radiating-member 26 hasahoie along" the axis thereof through which a -section of transmission hire 3? extends as will be hereinafter described. I

Theantenna arm 14- together with a second insuiating member 3 is also clamped to the junciion box-1'8 inamannersiniii ar to that just de- Scribd. v

Two antenna arms '56 and 38, in all respects similar to antenna arms 22 and it, are firmly eiampedtothe io'wer junction box 20in exactly the" some manner that the; upper antenna'arins "22* and 24 are oIampedt-o the junction box It. AH antenna arm-s are insulated from their respective innctiori boxesbyan insulating member similar to the member 28 describe above.

The active portion, of each antenna arm is substantially one-haii waveiength at the operat ing freqoenoy; Each is bentat-a point a! proximately atits center'- in the manner shown so that the two'inchnedportions of any one arm includes an'arigie'oi substantially I20". "l'hisarig'leis not eritie'afgand its exaet value is subject to determination by" experimentation.

so We have found, however, that inacoordanee with our invention an angle of substantially 120 produces the desired radiation pattern as illustrated in Fig. 4.

elements in a sense actually form part of the supporting structures themselves since they are positioned between members 8 and I U and the spacing member 6. The reflectors 40 and 42 are preferably welded to the members 6, 8 and I employed. The length of the reflecting elements.

40 and 42 are substantially one-half wavelength at the operating frequency and these reflecting elements are positioned from the co-linear portions of the bent antenna elements approximately one-quarter wavelength at the operating frequency.

The above lengths which have been given in terms of wavelength are subject to some variation due to the fact that the electrical length of any radiating structure is usually somewhat greater than its actual physical length. This'is due to end effects which tend .to increase the electrica1 length of a radiating member.

The plane which is defined by the bent antenna arms 22 and 24 together with the reflector Wis 4 arms .22 and 24 is in phase with the radiation from the lower antenna arms 36 and 38 radiation in the vertical direction is very low. This radiation would be substantially zero were it not for the difference in wave propagation along the transmission line and the wave propagation in free space. Due .to low downward radiation,

wave reflections from the ground or from other objects which may be located beneath the antennav structure are greatly reduced. Likewise,

: since all antenna arms are radiating in phase although other means of support could also be coincidence, the field pattern produced by our antenna structure is a. maximum in a general horizontal plane and to one side of the antenna structure due to the reflecting properties of the reflectors 40 and 42 as is well understood. Actually the surface of maximum radiation is not horizontal but inclines somewhat upwardly from the horizontal due to a certain amount of reflection from the earth's surface.

i It is recognized that due to reflections from the ground resulting from the so-called mirror image of the antenna there generally W l be veral lobes of radiation in the vertical plane. It is the lower lobe which is usually employed in determining the field pattern .for a glide path.

positioned substantially one-half wavelength from a parallel plane determined by the antenna arms 36 and 38 and the reflector 42. The actual separation of these planes is determined by the requirement that radiation from all the antenna arms are substantially in phase coincidence.

vational view of part of our antenna structure as viewed from the plane 33 in Fig. 2; The

junction box 20 has its cover removed to show the transmission line conductors within. The velocity of wave propagation along the line 44 is somewhat less than the velocity of Wave p flp gation in free space and therefore that portion of the transmission line 44 extending between the upper and lower sets of antenna arms is somewhat less than a one-half wavelength at the operating frequency as determined by the length of a one-half wave in free space.

From a point on the transmission line conductors 46 and 48 within the junction boxes l8 and 20 are soldered or otherwise connected short lengths. of transmission lines 52, 54. 56 and 58. As illustrated in Fig. 1, the short length of transmission line 52 extends from conductor 48 to a point 60 on the antenna arm 22 where it is soldered orotherwise connected The actual point of connection 6!! is positioned from the end 62 7 of the arm 22 by an amount determined: by the desired impedancemat'ch between the transmissionline and the antenna: arm 22.; All-of, the short lengths of transmission lines 52, 54,156 and 58 are similarly connected to their respective an- While we have described above the principles of ourinvention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of our invention as set forth in the objects thereof and in the following claims.

We claim: 1. A directive antenna structure comprising two bent antenna arms lying in a common plane, the length of each arm being substantially onehalf wavelength, each of said arms consisting of a first and a second portion inclined at an angle "to each other, the first portion of one arm being colinear with the first portion of the other arm, .a linear reflecting element, the length of said reflecting element being substantially one-half wavelength, said reflecting element being positioned substantially one-quarter wavelength from said colinear portions in said common plane and on the side of said colinear portions toward which said second portions extend, all of said lengths being in terms of the operating wavelength of said antenna system.

I 2. A directive antenna structure in accordance with claim 1 in combination with means for translating high frequency energy therewith, said translating means comprising a two conductor transmission line, one of said conductors being v, con nected to one of said arms and the other con- .duct'or being connected to the other of said arms. 11.3. A directive antenna structure in accordance withclaim 1 wherein the angle between the first and second portions of each of said antenna arms is. substantially l4. In combination, a directive antenna structure"and",energizing means therefor, comprising two bent antenna arms lying in a common plane, the length of each arm being substantially onehalf wavelength, each of said arms consisting of a first and a second portion inclined at an angle to each other, the first portion of one arm being colinear with the first portion of the other arm, a linear reflecting element, the length of said reflecting element. being substantially one-half wavelength, said reflecting element being positioned substantially one-quarter wavelength from said colinear portions in said common plane and on the side of said colinear portions toward which said'second portions extend, all of said lengths being in terms of the operating wavelength of said antenna, system, means for energizing said antenna arms, said energizing means comprising a balanced two conductor transmission line, one oi said conductors being connected to one end of one of said arms, the other conductor being connected to the adjacent end of the other of said arms whereby the radiated waves from said antenna arms are in phase coincidence.

5. A directive antenna system in accordance with claim 4 in combination with a second substantially identical antenna structure as that recited in said claim, said second structure being positioned substantially one-half wavelength from the first named structure, and means for energizing said identical antenna structure in phase coincidence with the first named antenna structure, said energizing means comprising a transmission line perpendicular to the planes of each of said antenna structures.

6. A directive antenna system in accordance with claim 4 in combination with a substantially identical antenna structure as that recited in said claim, said substantially identical structure being positioned a plurality of quarter wavelengths from the first named antenna structure, the plane passing through said reflecting elements being substantially perpendicular to the planes passing through said antenna structures and means for energizing both antenna structures whereby radiation perpendicular to the plane of said antenna, structures is substantially zero.

'7. A directive antenna system comprising a frame member, two bent antenna, arms lying in a common plane, the length of each arm being substantially one-half wavelength, each of said arms consisting of a first and a second portion inclined at an angle to each other, the first portion of one arm being colinear with the first portion of the other arm, a linear reflecting element conductively connected to said frame member, the length of said reflecting element being substantially onehalf wavelength, said reflecting element being positioned substantially one-quarter wavelength from said colinear portions in said common plane and on the side of said colinear portions toward which said second portions extend, all of said lengths being in terms of the operating wavelength of said antenna structure, insulating means for connecting said antenna arms to said frame member and means for energizing said antenna arms at the adjacent ends thereof whereby said arms radiate in phase coincidence.

CHESTER B. WATTS, JR. LEON HIMMEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,186,554 Perroux Jan. 9, 1940 2,281,429 Goddard Apr. '28, 1942 2,199,050 Jenkins Apr. 30, 1940 2,290,800 Brown July 21, 1942 2,292,791 Mims Aug. 11, 1942 FOREIGN PATENTS Number Country Date 11,3'17/33 Australia. May 17, 1934 

